The electrical conductivity and Seebeck coefficients of AgSbO₃ with a defect pyrochlore structure were investigated for evaluation as thermoelectric material. In sintering AgSbO₃, CuO was used as a sintering aid, and Cu substituted for Ag in the ceramic during the sintering. AgSbO₃ is an n-type semiconductor, and the addition of Cu increased electrical conductivity and decreased the absolute value of the Seebeck coefficient. The power factor of the 2.5% CuO-added sample was 7.24×10^-4 Wm^-1 K^-2 at 800°C. This value is one of the highest observed in oxide materials.